The present invention relates to a belt conveyor comprising an endless and closed conveyor belt, which is flexible essentially merely about axes, which are parallel with the transverse direction of the belt. This flexibility is a consequence of that the cross-section of the conveyor belt in the closed state thereof has a larger width, i.e. the dimension in the transverse direction of the conveyor belt, than height, i.e. the dimension of the conveyor belt perpendicular to said transverse direction.
A belt conveyor according to the present invention further comprises a tower, an inner arm supported by the tower, and an outer arm supported by the inner arm and positioned substantially in a vertical plane through the inner arm, the conveyor belt following a path from the tower, via the inner arm and the outer arm to a distal end of the outer arm and back via the outer arm and the inner arm to the tower.
Conveyor belts of the above type are described in, for instance, U.S. Pat. Nos. 5,060,787, 5,351,810 and 5,400,899, hereby incorporated by reference. The conveyor belt preferably is of a type disclosed in any one of these U.S. patents. Such a conveyor belt substantially consists of an elastic material, such as rubber, and comprises a planar central part, two planar edge parts and two hinge parts.
The central part is flexurally rigid about the longitudinal axis of the belt by means of a transverse reinforcement and has low extensibility in the longitudinal direction by means of a longitudinal reinforcement. Consequently, the outer side of this central part forms the pulling power take-up side of the conveyor belt, which preferably should make direct contact with each roller that the conveyor belt passes over.
The two planar edge parts are each hingedly connected with a side edge of the central part and flexurally rigid about the longitudinal axis of the belt by means of a transverse reinforcement. The edge parts are further extensible in the longitudinal direction of the belt and have a total width, which is at lest equal to the width of the central part, thereby enabling a complete closure of the conveyor belt.
The two hinge parts connect each edge part with the central part and are flexible about the longitudinal axis of the conveyor belt and also extensible in the longitudinal direction of the conveyor belt. Preferably, the hinge parts are further resilient for pivoting the edge parts out from a position folded towards the central part, and have a substantially smaller width than the central part.
In its closed state, the endless conveyor belt thus is flexible essentially merely about axes, which are parallel with the transverse direction of the belt. This flexibility is a consequence of that the cross-section of the conveyor belt in the closed state thereof has a larger width, i.e. the dimension in the transverse direction of the conveyor belt, than height, i.e. the dimension of the conveyor belt perpendicular to said transverse direction.
Thus, each one of these belts is designed to be bent, in its closed state, rather in the one than in the other direction about an axis parallel to its transverse direction. The conveyor belt should therefore be passed around a deflection roller with contact between one side of belt, i.e. the pulling power take-up side, and the deflection roller. In order to obtain this optimal positioning of the belt relative to a deflection roller, the belt may have to be twisted around its longitudinal axis 180xc2x0, which may require a substantial length making the belt conveyor larger than desired. Also, when parts of such a conveyor belt extend along parallel planes, a twisting of those parts results in a lateral bending thereof, i.e. a bending in a plane defined by the transverse and longitudinal directions of the conveyor belt, requiring a dynamic elastic deformation of the conveyor belt.
Belt conveyors of the above type are, among other things, used for loading and unloading of ships moored alongside a quay. The may also be used for conveying goods to or from a depot, on the ground, or to a depot within a silo.
One object of the present invention is to enable a reduction of the length or height of the known belt conveyors using conveyor belts of the above type while still following their optimal bending patterns.
Thus, two first deflection rollers for the conveyor belt are supported side by side at an intersection of the inner arm and the outer arm and have a common axis of rotation which is perpendicular to said vertical plane. Further, a first terminal roller for the conveyor belt is supported at a distal end of the outer arm and has an axis of rotation, which is positioned in said vertical plane. As a result, the conveyor belt need be twisted only 90xc2x0 in the paths between the first terminal roller at the distal end of the outer arm and each one of the two first deflection rollers at the intersection of the outer arm and the inner arm.
Preferably, the outer arm is pivotable in said vertical plane about an axis perpendicular to said vertical plane at an intersection of the outer arm and the inner arm.
Also, the inner arm preferably is pivotable in said vertical plane about an axis supported by the tower and perpendicular to said vertical plane. In this case, the tower should support two second deflection rollers for the conveyor belt side by side with an axis of rotation common to the axis supported by the tower for the pivoting of the inner arm.
A second terminal roller for the conveyor belt having an axis of rotation which is positioned substantially in said vertical plane, may be supported below the two second deflection rollers and closing the conveyor belt path.
Two third deflection rollers for the conveyor belt having a common axis of rotation parallel to the common axis of rotation of the two second deflection rollers, may be positioned between the two second deflection rollers and the second terminal roller, thereby enabling a shifting of the position of the second terminal roller in relation to the two second deflection rollers.
Two further deflection rollers having axes of rotation that are substantially parallel with said vertical plane, may be supported below the two second deflection rollers for deflection of the conveyor belt along a path extending substantially perpendicular to said vertical plane between two further terminal rollers. This will result in a belt conveyor which constitutes the single conveyor between a loading/unloading station and an unloading/loading station, i.e. requiring no transfer of the goods to another conveyor.
The conveyor belt may follow a path via at least one other deflection roller between each one of the second deflection rollers and the corresponding deflection roller of said further deflection rollers.
The tower may also be movable along a path extending perpendicular to said vertical plane.
Also, the tower may be rotatable about a vertical axis.
In this context, terminal roller is intended to mean a roller where the conveyor belt turns about 180xc2x0 while a deflection roller is a roller, which provides a less turn of the conveyor belt. Further, the conveyor belt should preferably pass around a terminal roller in an open state, i.e. carrying no load. However, the conveyor belt will pass around a terminal roller in a closed state if loading is made before, and unloading after passage of a terminal point. The belt can also be made to pass a terminal roller in a closed state in order to avoid dust or spillage.